JPH05100491A - Electrostatic charge image developing positive charge dry toner - Google Patents

Abstract

PURPOSE:To obtain a dry toner having a narrow charge distribution, and excellent stability of electrification for lapse of time by using carbon black of pH<=6.5 as a coloring agent and adding a specified compd. as a charge controlling agent. CONSTITUTION:The dry toner essencially consists of a binder resin and a coloring agent. As for the coloring agent, carbon black of pH<=6.5 is used, and as for a charge controlling agent, a compd. expressed by formula I or II is added. It is preferable to add silica fine particles treated with a quaternary ammonium salt as an external additive. In formulae I and II, R1-R5 are -CnH2n+1, formula III, or formula IV. By using a quaternary ammonium salt expressed by formula I or II and carbon black of pH<=6.5, more preferably pH<=6 and containing >=3% oxygen content, the quaternary ammonium salt as the charge controlling agent can be uniformly dispersed in a microscopic state. Thereby, the obtd. toner shows a narrow charge distribution and excellent stability of electrification for lapse of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positively chargeable dry toner for developing an electrostatic charge image used for developing an electrostatic latent image in electrophotography, electrostatic recording and the like.

[0002]

2. Description of the Related Art In electrophotography, a photoconductive substance such as selenium is used as a photoconductor to form an electric latent image by various methods, and a magnetic brush developing method or the like is applied to the electrostatic latent image. In general, a method is used in which toner is made to adhere to form a visible image. The developing toner used therein is charged by various friction charging methods and used in a state of holding a positive or negative charge depending on the polarity of the electrostatic latent image to be developed. By the way, the charging performance of the developing toner can be secured to some extent by the thermoplastic resin which is the main component of the toner, but it is not sufficient. When the chargeability of the toner is low, problems such as fog and the like in image characteristics and short life occur. Further, a method of positively charging by using neutral or weakly basic furnace type carbon (Japanese Patent Laid-Open No. 52-777).
No. 32) is also known, but similar to the above, sufficient charging cannot be obtained. That is, since channel black is acidic, it is not suitable for use in positively chargeable toner.

Therefore, conventionally, the above problem has been solved by adding a charge control agent to the toner. Examples of the charge control agent that imparts a positive charge include quaternary ammonium salts (for example, JP-A-49-5195).
No. 1). However, since the quaternary ammonium salt is water-soluble, it is difficult to uniformly disperse it in the toner. That is, the quaternary ammonium salt is likely to exhibit a micelle morphology due to the surfactant effect, and as a result, it is extremely difficult to disperse the quaternary ammonium salt in the binder resin in a micro-dispersed state, even if various kneading conditions are changed. there were. If the dispersion of the charge control agent in the toner is not uniform, the toner is not evenly charged and the distribution of the charge amount of the developer is widened, resulting in fogging and toner scattering. Further, the attenuation of the charge amount of the developer during copying becomes extremely large, which may cause variations in the density of the copy.
Further, the quaternary ammonium salt aggregate dispersion exposed on the toner surface has a drawback that water is easily taken in under high temperature and high humidity, and the charging performance is greatly affected.

[0004]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the problems in the above conventional techniques. That is, the object of the present invention is that the quaternary ammonium salt type charge control agent is uniformly dispersed in the binder resin, the charge amount distribution is narrow, the charge stability over time is excellent, and the environmental stability is high. To provide a dry toner.

[0005]

Means for Solving the Problems As a result of investigations, the present inventors have found that quaternary ammonium salts shown below and carbon black having a pH of 6.5 or less, preferably carbon having a pH of 6 or less and an oxygen content of 3% or more. By using black, a toner having a sufficient positive chargeability by dispersing a quaternary ammonium salt as a charge control agent in a microscopic form was found, and the present invention was completed.

The dry toner of the present invention contains a binder resin and a colorant as main components, and as the colorant, P is used.
A carbon black of H6.5 or less is used, and a compound represented by the following formula is added as a charge control agent,
Preferably, positively-charged silica is externally added.

[0007]

[Chemical 2]

The present invention will be described in detail below. When dispersing carbon black in the binder resin, it is possible to control the dispersion to some extent by the kneading conditions (shear strain control). In particular, carbon black having a pH of 7 or less has good dispersibility in a resin because it has a polar group. In the present invention, the dispersibility is improved by using PH6.5 or less, preferably PH6 or less.

Carbon black having a pH of 6.5 or less has polar groups (-OH, -COOH,> C = O, -C) on its surface.
(= O) H and the like, and polar groups (particularly -O) of the counter ion of the quaternary ammonium salt are present in these polar groups.
H) undergoes some interaction, whereby the dispersion of the quaternary ammonium salt, which is the charge control agent, is affected by the dispersion of carbon black, or the charge control agent is less likely to exhibit a micellar structure and exhibits microdispersion. Like Therefore, a positively chargeable toner having a very narrow charge amount distribution and very little environmental dependency can be obtained. In the present invention, more preferably, positively-charged treated silica treated with a quaternary ammonium salt is added as an external additive. As a result, the active polar groups of carbon black appearing on the toner surface are hidden, and a toner having little environmental dependence and good powder fluidity can be obtained.

Examples of the quaternary ammonium salt type charge control agent used in the present invention include the following, but the present invention is not limited thereto.

[Chemical 3]

In the present invention, the compounding ratio of the quaternary ammonium salt is not particularly limited, but the binder resin 100 is used.
It is preferable to add 0.1 to 5.0 parts by weight with respect to parts by weight.

Examples of the binder resin used in the developing toner of the present invention include styrenes such as styrene, chlorostyrene and vinylstyrene; ethylene, propylene, butylene,
Mono-olefins such as isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate,
Ester of α-methylene aliphatic monocarboxylic acid such as butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, vinyl ethyl Examples thereof include vinyl ethers such as ether and vinyl butyl ether; homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone. As typical binder resins, , Polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene Polypropylene can be mentioned. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin and waxes can be mentioned. The binder resin used in the dry toner of the present invention is not limited to the above resins, and any resin can be used as long as it meets the object of the present invention.

As the colorant, carbon black having a pH of 6.5 or less, preferably PH6 or less and an oxygen content of 3%
The above channel blacks are preferably used. Specific examples thereof are shown below, but the invention is not limited thereto. BLACK PEARLS 1
300, Black Pearls
S) 1000, Black Pearls (BLACK PEA
RLS) L, Royal Spectra (ROYAL SP
ECTRA), Neo Spectra Mark (NEO SPE)
CTRA MARK I, Neo Spectra Mark (NE
O SPECTRA MARK II, NEO SPECTRA AG, Super (SUPE)
R) BA (NEO MK III), Neo Spectra Mark (NEO SPECTRA MARK) IV, Cabot Co., Raven (RAVEN) 8800, Raven (RAVEN) 8000, Raven (RAVEN)
7,000, Raven 5750, Raven 5250, Raven 3
500, RAVEN 1800, RAVEN 1255, RAVEN 10
85 BEADS, RAVEN 1040, RAVEN 825 BEADS, manufactured by Colombian and the like. These carbon blacks are added in an amount of 3 to 20 parts by weight, preferably 6 to 12 parts by weight.

The binder resin and the colorant are not limited to those exemplified above. The dry toner of the present invention may be a magnetic toner containing a magnetic substance or a capsule toner. In the dry toner of the present invention, the above materials are mixed by using a Banbury mixer, a kneader coater, a CM mixer, an extruder or the like, melt-kneaded, pulverized and classified to have an average particle size of about 30 μm or less, preferably 3 to 20 μm. Of fine particles. Various additives may be added to the dry toner of the present invention, if necessary. Examples of the additive include a charge control agent, a magnetic substance, a cleaning aid, a fluidity promoter, and the like.

The toner of the present invention is used for developing an electrostatic latent image formed on a photoconductor or an electrostatic recording medium. The toner of the present invention is used as a one-component developer or a two-component developer. When used as a two-component developer, a known carrier such as ferrite iron oxide powder nickel, a coated carrier obtained by coating these with a resin, or a magnetic powder dispersion type carrier can be used. That is, an electrostatic latent image is electrophotographically formed on a photoreceptor made of an inorganic photoconductive material such as selenium, zinc oxide, cadmium sulfide, or amorphous silicon, or an organic photoconductive material such as a phthalocyanine pigment or a bisazo pigment. An electrostatic latent image is formed on the electrostatic recording material having a dielectric material such as polyethylene terephthalate by a needle-shaped electrode or the like, and the electrostatic latent image is formed by a developing method such as a magnetic brush method, a cascade method, or a touchdown method. The dry toner of the present invention is applied to form a toner image. This toner image is transferred to a transfer material such as paper and then fixed to form a copy, and the toner remaining on the surface of the photoconductor or the like is cleaned by a known cleaning device such as a cleaning blade or a cleaning roll.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Example 1 Styrene-butyl methacrylate copolymer (copolymerization ratio 80/20, 100 parts by weight Mn: 5000, Mw: 250,000) Carbon black BP-1300 (manufactured by Cabot) 10 parts by weight (PH = 2.5, Oxygen content 9.5%) Low molecular weight polypropylene 660P (manufactured by Sanyo Kasei Co., Ltd.) 5 parts by weight Charge control agent (exemplified compound (1)) 2 parts by weight <PH measurement> Samples 1 to 10 g are weighed in a beaker to prepare a sample 1 g. Add water at a rate of 10 ml, cover with a watch glass, and boil for 15 minutes. After boiling, the mixture is cooled to room temperature and the supernatant is removed by a gradient method or a centrifugal method to leave a mud. An electrode of a glass electrode PH meter is put in this mud and the PH is measured according to JIS Z8802. The measurement is carried out three times by stirring with a stirring rod so that the mud-like matter adheres well to the periphery of the electrode, and this operation is repeated until the range of the measured value becomes 0.1 or less. <Oxygen content> heating the carbon black, taken as volatiles as _(C x _{O y).} The substance is quantified by elemental analysis.

A toner kneaded product was obtained by continuously kneading the above composition using an extruder, and then pulverizing and classifying D
A toner of ₅₀ = 9.0 μm was obtained. To 100 parts of the above toner, 2 parts of titanium oxide having an average particle diameter of 0.1 μm was used and mixed with a Henschel mixer to obtain a toner containing an external additive. On the other hand, a carrier having a D ₅₀ = 50 μm obtained by melt-kneading a styrene-butyl methacrylate copolymer (composition ratio 80/20) and magnetic powder, pulverizing and classifying was used. A developer composition was prepared by mixing 95 parts of this carrier with 5 parts of the toner containing the external additive.

Example 2 Instead of the carbon black of Example 1, Raven (R
AVEN) 1255 (Colombian): (PH =
2.5, oxygen content 3.5%) A developer composition was prepared in the same manner as in Example 1 except that 10 parts by weight was used.

Example 3 Black pearls (BLACK PEALS) L (manufactured by Cabot), 10 parts by weight (PH = 3, oxygen content 5.0%) were used in place of the carbon black of Example 1. A developer composition was prepared in the same manner as in Example 1.

Example 4 In Example 1, as an external additive, silica (R97
2; 90 parts of Nippon Aerosil Co., Ltd.) and 10 parts of a charge control agent (exemplified compound (1)) (dissolved in twice the amount of alcohol) were used in a fluidized bed. A developer composition was prepared in the same manner as in Example 1, except that 1 part of the treated silica was added to 99 parts by weight of the toner and the externally added toner was obtained with a Henschel mixer.

Comparative Example 1 Instead of the carbon black of Example 1, legal (R
EGAL) 330 (manufactured by Cabot), PH = 8.
5, the oxygen content = 1.5%) was used to prepare a developer composition in the same manner as in Example 1.

Comparative Example 2 Instead of the charge control agent in Example 1

[Chemical 4] A developer composition was prepared in the same manner as in Example 1 except that was used.

Comparative Example 3 A developer was prepared in the same manner as in Example 1 except that the charge control agent in Example 1 was not added. These were evaluated. The results are shown in Table 1.

[0024]

[Table 1]

(1) X using a TEM (Hitachi H-950)
The internal dispersion structure was observed at 9000. (2) FX-5075 was used for the actual machine evaluation under high temperature and high humidity 3
An evaluation test was performed at 0 ° C 90% and at low temperature and low humidity at 10 ° C 20%. (3) TC latitude; after the 100,000 sheets have been copied (under normal environment), toner is forcibly added to cause fogging.
C was taken as Tch, then dispensed, cut and collected, TC showing 1.0GSAD → 1.1 was taken as Tcl, and TC latitude was evaluated as Tch-Tcl.

[0026]

INDUSTRIAL APPLICABILITY In the present invention, carbon black having a pH of 6.5 or less is used as the colorant as described above, and the charge control agent as exemplified is used. A dry toner is obtained. As a result, the positively chargeable dry toner of the present invention has very little environmental dependence, has a fast charging start-up even when the toner is forcibly added, and is very stable in charging, and has high reliability. Is.

Continuation of front page (51) Int.Cl. ⁵ Identification number In-house reference number FI Technical display location 7144-2H G03G 9/08 375 (72) Inventor Takayoshi Aoki 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Zero Tsukus Takematsu, Ltd. Inside the office

Claims (2)

[Claims] 1. A dry toner containing a binder resin and a colorant as main components, wherein carbon black having a pH of 6.5 or less is used as a colorant, and a compound represented by the following formula is added as a charge control agent. Positively chargeable dry toner for electrostatic image development. [Chemical 1] 2. The positively chargeable dry toner for developing an electrostatic charge image according to claim 1, wherein silica fine particles treated with a quaternary ammonium salt are added as an external additive.